In this VETgirl online veterinary continuing education blog, Amy Newfield, CVT, VTS (ECC) reviews blood lactate in veterinary medicine, and how it is often an under utilized diagnostic tool in the emergency room for the critically ill patient!

Blood Lactate: The Under Utilized Diagnostic Tool
By Amy Newfield, CVT, VTS (ECC)

Monitoring blood lactate is a standard in the human healthcare industry and while it is routinely utilized in veterinary specialty medicine, it is not found often in general practices.

What is Blood Lactate?
Blood lactate is a by-product of anaerobic glycolysis. All cells in the body work on aerobic processes. When oxygen is inadequately delivered to cells lactate is built up. As blood lactate increases it can be used as a biomarker to indicate that inadequate perfusion and oxygenation of cells within the body is occurring.

There are two types of hyperlactatemia: Type A and Type B lactate. Type A hyperlactatemia occurs because of tissue hypoperfusion while Type B occurs from a cellular dysfunction not being able to utilize the oxygen delivered or perhaps a decrease in clearance. Regardless of the cause, when blood lactate increases it indicates that cells are in an anaerobic state. Under 2.5 mmol/L is considered normal in dogs and cats. Anything above 2.5 mmol/L is an indication of hyperlactatemia and the cause should be investigated.

Why is Blood Lactate Important?
I once had a patient who was suffering from hemorrhagic gastroenteritis. The Labrador retriever was five years old and had gotten into the trash the day before. The patient looked clinically depressed, but his physical exam findings were normal:

HR: 90 bpm, NSR
Pulses: Strong and synchronous
RR: 32, no effort, clear lungs
T: 100.2 °F
MM: Pink
CRT: <2 seconds
BP: 110 mmHg systolic (performed via Doppler)

The patient also appeared adequately hydrated and had a soft, non-painful abdomen. The hematochezia wasn’t that often or that plentiful. However, here was my patient looking depressed, curled up in a sad dog ball, not even wanting to pick up his head to see what was going on. After some discussion we decided to perform a blood lactate. His blood lactate was 7.2 mmol/L. Despite our best efforts to rehydrate our patient we had not done enough. He needed more fluids because he was still in an anaerobic state. Outwardly he appeared fine, but inwardly his cells were saying “we are not happy!” After more intravenous fluids our patient was barking and bounding around like the happy Labrador is was.

How to Measure Blood Lactate
There are several point of care instruments available. Many look just like a blood glucose machine and are handheld. They require the same size drop of blood as a blood glucose machine. Many larger chemistry analyzers now include blood lactate as a measurement you can add on to the chemistry you are running. Blood gas analyzers not often include lactate as a standard biomarker to measure.

The monitoring of serial blood lactate in human medicine is considered a main biomarker to measure for most patients. Human medicine has studied blood lactate levels extensively proving that elevations for some disease processes over a certain reading indicates increases in morbidity and mortality. They tailor their treatments and nursing care based on the blood lactate levels. Veterinary medicine has really only started to incorporate blood lactate in the past 15 years. While the studies are limited compared to that in human medicine, veterinary medicine studies have shown that blood lactate can be used to drive the care of a patient towards a more favorable outcome and even provide a better prognosis for the patient’s outcome.

How to Treat Hyperlactatemia
The underlying cause of the increased lactate must be investigated. Usually the hyperlactatemia is an indication of hypoperfusion so addressing perfusion issues through additional fluid support or supporting blood pressure with vasopressors is important. All veterinary clinics should utilize lactate for veterinary patients with illness or injury. General practices that have a hit by car trauma patient that arrives at the hospital should monitor lactate. Despite all physical exam and blood pressure parameters being normal, the patient may still need aggressive fluid support in order to reverse the shock and get the perfusion of that patient back to normal.

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